This invention relates to multiple pump assemblies for operating fluid powered equipment in a motor vehicle or the like.
The combination of a vane pump and a radial piston pump in tandem for supplying two separate fluid circuits is already known, as disclosed for example in prior German patent application DE-PS 28 03 772. In such an arrangement, the drive shafts of both pumps are coupled with each other by means of a cross-disc coupling. Each pump has its own suction connection to a common fluid reservoir tank. By way of example, the vane pump supplies pressurized fluid to a fluid powering steering circuit while the radial piston pump supplies pressurized fluid to a fluid powering brake circuit associated with a motor vehicle. According to such prior pump arrangements, the vane pump requires a relatively high energy input as the power output demand increases proportionately with the increase in pump speed. The volumetric output of the vane pump is therefore adjusted for a relatively low pump speed by a control valve on the output pressure side of the pump.
In plural pump arrangements of the foregoing type, the consumption of input energy is somewhat wasteful. Measures ordinarily taken to conserve energy generally involve the addition of costly components. Furthermore, in such plural pump arrangements, pressure pulsations developed in one of the fluid circuits is transferred to the other of the fluid circuits.
It is therefore an important object of the present invention to provide a pump arrangement assembled from two or more pumps which consumes a minimum amount of energy and wherein manufacturing costs are maintained at a minimum. An additional object in accordance with the foregoing object is to provide a plural pump arrangement servicing plural fluid pressure circuits without mutual interference between such circuits caused by pressure pulsations in one of the circuits.